Page 20 - Mobility Management, April 2018

ATP Series
Functional Comfort
What a “Softail” Suspension System Can Do for Your Clients
By Elisha Bury
Suspension, a word built for automobile chassis and screaming motorcycles, matters more to a power wheelchair than one might think. It’s no accident that suspension systems are well debated in the motorcycle industry, after all. For these riders the difference between a “softail” and a “hardtail” is not only about comfort — it’s a de ning feature. Are you part of the new generation, wanting a comfortable ride built for distance? Or are you old school, gravitating toward a rigid “hardtail” so that you can feel the road?
For power chair users, suspension systems can provide similar de nition. The power chair might not be built for the highway, but its users never get off the bike. Turns out, the distance between “comfortable ride” and “clinically bene cial” is surpris- ingly short. The suspension system is pivotal to both. Mobility Management asked power chair suspension experts to tell us why.
Staying on Traction
Originally built as a bicycle with a motor, the motorcycle needed something its power-less ancestor did not have — a force to keep the tires in contact with the road. The power wheelchair — a chair with a motor — must have the same considerations. As such, the utilitarian purpose of suspension can be summed up as traction.
20 APRIL 2018 | MOBILITY MANAGEMENT
“In the absence of a suspension, the chair can ‘high-center.’ This is the condition where the drive wheel loses contact with the ground due to uneven surfaces. The suspension should allow the casters and drive wheel to move free enough for the drive wheel to remain in rm contact with the ground, ensuring mobility,” says Dan Critch eld, product manager for Sunrise Medical’s power line.
To accomplish this, power wheelchair suspension systems incorporate tires, casters, swing-arms and springs to absorb shock and vibration.
“The larger, wider and softer a tire is, the softer or ‘better’ the ride,” says Brad Peterson, VP of Professional Affairs and Clinical Education for Invacare Corp. “Power wheelchairs with pneumatic tires and casters provide a softer ride, but they require upkeep to maintain the optimal performance. And there are also concerns with durability and reliability. Furthermore, a larger front caster on rear-wheel-drive and mid-wheel-drive (chairs) will provide a better ride and more obstacle-climbing capability, but the trade-off is front-rigging positioning and caster interference.”
In fact, different suspension designs often require a trade-off, Peterson explains. But all suspension systems “work differently based upon drive-wheel position, geometry of the power base
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